Rewriting git commit authorship

This is a short note about rewriting the history of a git repository to change the commit authorship.Posted by Thomas Sutton on October 24, 2013

Here’s a quick guide to rewriting the history of a git repository to correct commit authorship. I’ve found this useful when committers use multiple machines with different user.name and user.email configurations and they need to be brought into line.

The first example is useful to “fix” commits which have been made with the wrong author name and email. I’ve sometimes seen this when people use git for deployment and make an “urgent” fix on a production servers and commit as “web-owner@web3.example.com”.

Rewriting all commits that have email web-owner@web3.startup.com to have the name “Thomas Sutton” and e-mail “me@thomas-sutton.id.au” is simple:

If this is a regular problem for you, you might want to rewrite all commits with an email address that does not match some pattern. If your pattern can be written as a glob you can use the built-in pattern matching functionality in bash:

Here I’m rewriting every commit where the email address does not match *@examplecorp.com to have the name “Example Corp” and email address tech@examplecorp.com. Notice that this example uses double square brackets around the condition: [[ ]]. It’s this change that enables pattern matching as opposed to the single brackets and simple equality in the first example.

You need to remember, though, that techniques like this rewrite the complete history of the repository. This means that all other branches, all clones, etc., etc. will all need to be re-done to match with this new history. Do not do this unless you know what this warning means and how to resolve any issues you’ll have.

This post was published on October 24, 2013 and last modified
on June 4, 2020. It is tagged with: git, howto, rewrite, history.